This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-327514 filed on Oct. 25, 2001.
The present invention relates to an instrument panel unit of a vehicle, which incorporates a radio signal wave receiver such as a keyless entry receiver.
Recent automobiles have radio signal receivers besides car radio receivers. These receivers are typically used for keyless entry systems. The keyless entry system is a vehicle control system for implementing door lock/unlock, etc. It includes a keyless entry receiver equipped on the vehicle and a keyless entry transmitter concealed in the key of a vehicle, etc. held by a vehicle driver.
The keyless entry transmitter is activated by the driver to send out a modulated signal including an ID code unique to the transmitter and an operation command code. The keyless entry receiver which receives a radio signal demodulates the signal to determine whether it is from the paired transmitter. In response to the signal relevancy, it releases a control signal derived from the operation command code to a corresponding ECU of vehicle by which the door lock/unlock, engine start, etc. is carried out.
The keyless entry system is generally based on a weak radio signal of 300-MHz band. The keyless entry receiver in the vehicle includes a radio signal antenna which is integrated with a circuit board of the keyless entry receiver.
In order for the keyless entry system to operate reliably in response to the signal from the paired keyless entry transmitter operated by the driver who is out of the vehicle, it is necessary for the keyless entry receiver to be sensitive enough to demodulate the radio signal including ID code and operation command code accurately.
JP-A-8-216735 discloses an instrument panel unit, with a radio signal receiver being incorporated, for indicating the vehicle speed, etc. This instrument panel unit has its radio signal receiver located near the windshield so that the receiver is less subject to the electromagnetic shielding effect of the metallic vehicle body. On the other hand, the keyless entry receiver which is fitted off the vehicle body must be grounded to the vehicle body through a wire harness. It is difficult to have low-impedance grounding. Therefore, the keyless entry receiver suffers fluctuation of antenna gain and directivity caused by nearby instrument circuit boards even though the receiver has an improved environment of signal reception.
On this account, the above instrument panel unit is impractical in attaining the adequate signal receiving performance.
In view of the foregoing situation, it is an object of the present invention to provide an instrument panel unit of a vehicle, which has a radio signal receiver that provides adequate and practical signal receiving performance.
According to the present invention, an instrument panel unit of a vehicle comprises a meter housing, a display section provided in the meter housing, a meter circuit provided in the meter housing and formed on a meter circuit board, and a radio signal receiver provided in the meter housing and formed on a receiver circuit board connected with an antenna.
The receiver circuit board has an inlet for the antenna in one of outer regions of the meter circuit board, at an upper side of the meter circuit board, or right above an electrically separated signal receiving pattern formed on the meter circuit board.
The antenna has segments, which extend in parallel to a surface of the meter circuit board, with a part of the antenna segments nearer to the inlet being extended in a longitudinal direction of the meter circuit board.
The meter circuit board has a circuit pattern, which is laid along a whole rim section of the meter circuit board to form a closed-loop radio signal receiving pattern at least with respect to RF circuit characteristics.